In conventional medical imagers or photo-thermographic recording apparatuses, the medical imager is structured so that each size of photo-thermographic films (film will be used hereinafter) of 17×14 inch size, 14×14 inch size and 11×14 inch size are processed in a single photo-thermographic recording apparatus by conveying the film in the direction being a right angle against 14 inch width direction of the film. And with regard to another size, for example, an 8×10 inch size film is processed by a dedicated photo-thermographic recording apparatus. There are no big differences between them, whichever the system is used, from the viewpoint of functions, performances and cost of the apparatus.
However, in recent years, needed is an imager capable of processing of 8×10 inch size film, etc., which has different sizes in a width direction and a longitudinal direction from that of the films described above, such as 17×14 inch size, 14×14 inch size and 11×14 inch, in a single apparatus.
In an imager employing a photo-thermographic process, there are problems specifically associated with photo-thermographic developing device which will be described below. Namely, in a photo-thermographic process, in case that a film is conveyed as the film is sandwiched by a heating drum and a plurality of opposed rollers as a means for heating and conveying the film, an elastic layer of silicon rubber, etc., is provided on the surface of a heating member to realize uniform contact between the film and the heating drum and the opposed rollers, and the uniform surface temperature of the heating drum, which is disclosed in Japanese Patent Application Open to Public Inspection No. H10-500497.
However, organic acid and/or higher fatty acid included in the photo-thermographic film volatilized by the heat drifts around the elastic layer, attacks the silicon layer and harms the cross-linking of silicon rubber as the photo-thermographic film is processed. Also, volatilized organic acid, etc., coheres and adheres onto the surface of the heating drum. Once these cohered substances form a film footmark on the surface of the heating drum, an image may be affected by these cohered substances.
Further, cutting dross from the leading edge, rear edge and side edges of the cutting surface of the film and emulsion flakes, etc., are adhered onto the heating drum and the opposed rollers. These substances harm the uniform contact or uniform thermal transmission and resulting density unevenness of the image.
Further more, a portion of the elastic layer where the film passes swells as the heating drum itself repeats heating and cooling. As a result, a crack starts to appear on the surface of the elastic layer and the crack is transferred onto the film. This phenomenon occurs since the contact condition between the heating drum and the film becomes uneven and the heat transmission across the heating drum becomes uneven. In case that a film conveyance pass in a thermal developing device is always unchanged, for example, 14 inch size, the image is formed without seriously affected and the heating drum properly operates until cracks occurs in the elastic layer even though 17×14 inch size film, 14×14 inch size film and 11×14 inch size film are processed.
However, in case that another size film which is different from 14 inch size film is processed in a single imager (a photo-thermographic recording apparatus), there has been problems that a swelling mark and/or a passing mark corresponding to the edge of the film occurs at a portion being different from 14 inch width-edge. Accordingly, when the maximum size film is processed, these marks described above appear in the image on the film.
In order to prevent those problems described above, cleaning was needed. However since a cleaning cycle becomes frequent and maintenance time and cost increase, it is not preferable to do so.
Japanese Patent Application Open to Public Inspection No. H11-65070 discloses an image recording apparatus which delays the conveyance of the new film being inputted into a thermal developing device, when the new film is a different size form a previous film, by holding the new size film for a predetermined time period. It discloses an image recording apparatus designed to unify the surface temperature of the heating drum by continuing rotation and heating of the heating drum by a heater while holding the new size film which will be inputted into the thermal developing device. However, it is not an image recording apparatus capable of removing the problems associated with the heating process of the photo-thermographic film.
It also discloses a photo-thermographic recording apparatus for removing dirt adhering onto a heating drum and preventing doted image defects by providing a dirt removing means having stickiness on the surface of the dirt removing means to be in contact with the heating drum, when visualizing an image formed on a photo-thermographic film by sandwiching the film between the heating drum and an endless belt in a heating device. However, it does not disclose the affection of foreign matter to the opposed roller and the cleaning of the opposed roller which is an auxiliary means operating together with the heating device.